The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
In the prior art, reinforcements and/or brackets are fastened to panels, in particular glass panels, to increase their stiffness. This is done by means of either a PU (polyurethane) gluing process, or an encapsulating process using PU low pressure injection molding.
In the gluing process, the surfaces to be connected are prepared and are provided with glue which should be cured for a long time, several hours, after the surfaces have been put together. The curing process should take place under the influence of the humidity in the air in a conditioned environment. No mechanical load can be exerted on the glued parts during the securing process.
In the encapsulating process, the parts to be connected are inserted into a tool/mold, after which the PU encapsulation is provided in a low pressure injection molding process. The reinforcements and/or brackets are surrounded at least partly by the PU material. After a short time lapse, a few minutes depending on the amount of encapsulating material and glass area, the assembly can be removed from the tool, and the product should be finished in order to remove films and injection residues along the edges of the encapsulation. The product is then immediately ready to be loaded.
An important characteristic of a (glass) panel assembly in a vehicle roof construction is the stiffness of the panel. Stiffness is required to prevent an excessive bending of the panel in conditions in which the dynamic pressure on the outside of the panel is much lower than on the inside. Such a pressure difference, which may be present at high vehicle speeds, can lead to seal malfunction at the edges of the panel, and therefore a noise problem, if the panel is not sufficiently rigid.
The stiffness of a panel in which the reinforcement is glued to the panel is less than that of encapsulated reinforcement, assuming that the reinforcements are equally rigid. In order to create a sufficient rigidity in glued reinforcements, the reinforcements and/or brackets should be made even more rigid, which means more height, which is unfavorable as it leads to head room loss for the vehicle passengers.
A disadvantage of the encapsulation process is that the material is relatively expensive and also the encapsulating tools require higher investments.